Photosensitive structure for flexographic printing

ABSTRACT

A photosensitive structure for flexographic printing having a support (A) and, laminated thereon, an adhesive layer (B) and a photosensitive resin layer (C) different from said adhesive layer (B), wherein said adhesive layer (B) is an adhesive layer (B) comprising a thermoplastic elastomer (a) derived from at least one monovinyl substituted aromatic hydrocarbon and a conjugated diene, at least one ethylenically unsaturated compound (b) and at least one polymerization initiator (c), wherein said ethylenically unsaturated compound (b) comprises at least one (meth)acrylate (i) having one or more aromatic rings and/or one or more hydroxyl groups in the molecule thereof.

TECHNICAL FIELD

1. Incorporation by Reference

The present application claims priority based on Japanese PatentApplication No. 2003-146713 filed on May 15, 2003, which is incorporatedin the present application by referring the contents thereof.

2. Technical Field

The present invention relates to a photosensitive structure forflexographic printing used for making a flexographic plate and a methodfor production thereof.

BACKGROUND ART

An ordinary photosensitive structure for flexographic printing has aconstitution wherein a polyester film is used as a support, and aphotosensitive resin is laminated thereon. A method for preparing aplate from a photosensitive structure for flexographic printing adoptssteps for exposing an image (relief exposure) on the surface of aphotosensitive resin through a transparent image carrier (negativefilm), washing away unexposed portions using a solvent for thedeveloper, and forming a desired image, i.e., a relief image, to obtaina printing plate. Furthermore, a method wherein the entire surface of aphotosensitive resin is exposed to ultraviolet rays through a support(back exposure) to form a thin evenly cured layer, and then reliefexposure is performed through a negative film, is also adopted. Thethickness of a flexographic plate is usually 0.5 to 10 mm, and thethickness of the plate is suitably selected depending on materials to beprinted and the setting of printers.

Although the obtained flexographic plate is used by fixing it on theplate cylinder of a printing machine using a double-sided adhesive tapeor the like, a shear stress is produced during printing in the printingplate between the plate cylinder and the impression cylinder. When theprinting plate is peeled from the support by the shear stress, a problemin that printing must be stopped or the like is caused. In addition,when the printing plate is removed from the plate cylinder afterprinting, the photosensitive resin may be peeled off the plate cylinderby pulling, and in such a case, the photosensitive resin and the supportare undergone stress. If the support and the photosensitive resin arepeeled off, the plate cannot be reused, and another plate must beprepared anew.

From such a point of view, a polyester film, which is a support, and thephotosensitive resin must be firmly adhered to each other, and theadhesive strength thereof is preferably 5.9 N/cm or more when thephotosensitive resin is forcibly peeled off the support at a peelingangle of 180°. Furthermore, from the viewpoint of the reuse of theplate, it is more preferable that the adhesive strength of 5.9 N/cm ormore is maintained even after the photosensitive resin is processed toprepare the plate and is aged.

From such a point of view, methods for forming an adhesive layer betweena support and a photosensitive resin layer are proposed in, for example,Patent Document 1 (JP-A-2000-155410) and Patent Document 2(JP-A-2001-264959). However, in these references, there is limitation inthe number of unsaturated bonds of an ethylenically unsaturated compoundcontained in the photosensitive resin layer, and for the photosensitiveresin layer composed of a photosensitive resin composition containing noethylenically unsaturated compounds described in these references, noneof adhesive layers exhibiting a good adhesive strength are described.

In Patent Document 3 (JP-A-4-204447), a photosensitive resinrelief-printing material provided with a photo-cured barrier layer to anink-washing oil on an adhesive-treated support. However, in this case,since an adhesive layer is formed, and a barrier layer is further formedthereon, the step for preparing the photosensitive resin printingmaterial becomes complicated.

As a material for a flexographic plate, Patent Document 4(JP-A-1-296252) proposes the intervention of an undercoat layer betweena support and an adhesive layer. Even in this case, since two layers ofthe undercoat layer and the adhesive layer are laminated, the step forpreparing the flexographic plate material becomes complicated.

In Patent Document 5 (JP-A-2-8849) and Patent Document 6 (JP-A-2-8851),a plate composed of at least one intermediate layer formed on a supportand a photosensitive relief layer formed on the intermediate layer isproposed. In these references, although polyvinyl alcohol and polyamideare shown as a binder used as the intermediate layer, a thermoplasticelastomer composed of a monovinyl substituted aromatic hydrocarbon and aconjugated diene is not described.

In Patent Document 6, although an intermediate layer that contains aspecific compound is described, the specific compound is monofunctional,and no polyfunctional compounds are described. Further as the effect ofthe invention, improved adhesiveness and the improvement of developersare described, the resistance to ink solvents required when used as aplate is not described.

In addition, a method relating to the reuse of the rejected plateproduced in the production of a flexographic plate is proposed in PatentDocument 7 (JP-A-6-214378). In this document, there is described thereuse consisting of a step for isolating a recording layer from asupport, a step for pulverizing the recording layer as required, and astep for adding the pulverized material to a synthetic resin mixture.However, the reuse requires a large number of steps, and has becomecomplicated.

As described above, it is the present situation that no photosensitivestructures for flexographic printing that has high adhesive strength andexcels in production efficiency, and the rejected plate produced in theproduction process can be easily reused have been found.

Patent Document 1: JP-A-2000-155410

Patent Document 2: JP-A-2001-264959

Patent Document 3: JP-A-4-204447

Patent Document 4: JP-A-1-296252

Patent Document 5: JP-A-2-8849

Patent Document 6: JP-A-2-8851

Patent Document 7: JP-A-6-214378

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

An object of the present invention is to provide a photosensitivestructure for flexographic printing that has a high adhesive strengthand excels in production efficiency, and the rejected plate produced inthe production process can be easily reused. A further object of thepresent invention is to provide a photosensitive structure forflexographic printing that excels in the stability of adhesive strengthwith time, produces no unevenness of adhesive strength in the plate, andhas an adhesive layer with excellent resistance to ink solvents.

Means for Solving the Problems

The present inventors conducted keen examinations on the above-describedproblems, and found that the above-described problems could be solved bydevising adhesive layers, and completed the present invention.Specifically, the present invention is as follows:

-   (1) A photosensitive structure for flexographic printing formed by    laminating a support (A), an adhesive layer (B) and a photosensitive    resin layer (C) different from the adhesive layer (B), wherein the    adhesive layer (B) contains a thermoplastic elastomer (a) derived    from at least one monovinyl substituted aromatic hydrocarbon and a    conjugated diene, at least one ethylenically unsaturated    compound (b) and at least one polymerization initiator (c), wherein    the ethylenically unsaturated compound (b) has at least one    (meth)acrylate (i) having one or more aromatic rings and/or one or    more hydroxyl groups in the molecule thereof.-   (2) The photosensitive structure for flexographic printing according    to (1), wherein the (meth)acrylate (i) comprised by the    ethylenically unsaturated compound (b) and having one or more    aromatic rings and/or one or more hydroxyl groups in the molecule    thereof has two or more ethylenically unsaturated groups.-   (3) The photosensitive structure for flexographic printing according    to (1) or (2), wherein the (meth)acrylate (i) comprised by the    ethylenically unsaturated compound (b) and having one or more    aromatic rings and/or one or more hydroxyl groups in the molecule    thereof has a bisphenol skeleton.-   (4) The photosensitive structure for flexographic printing according    to any of (1) to (3), wherein the ethylenically unsaturated    compound (b) contains a (meth)acrylate (i) having one or more    aromatic rings and/or one or more hydroxyl groups in the molecule    thereof, and a polyester (meth)acrylate (ii) having two or more    ethylenically unsaturated groups in the molecule thereof.-   (5) The photosensitive structure for flexographic printing according    to any of (1) to (4), wherein the ethylenically unsaturated    compound (b) contains a (meth)acrylate (i) having one or more    aromatic rings and/or one or more hydroxyl groups in the molecule    thereof, and a polyester (meth)acrylate (ii) having two or more    ethylenically unsaturated groups in the molecule thereof; wherein    the weight ratio (i):(ii) is 0.01:1 to 10:1.-   (6) The photosensitive structure for flexographic printing according    to any of (1) to (5), wherein the thickness of the adhesive    layer (B) is 0.0001 to 1 mm.-   (7) The photosensitive structure for flexographic printing according    to any of (1) to (6), wherein the photosensitive resin layer (C) is    a mixture of a thermoplastic elastomer derived from at least one    monovinyl substituted aromatic hydrocarbon and a conjugated diene,    at least one ethylenically unsaturated compound, and at least one    polymerization initiator.-   (8) The photosensitive structure for flexographic printing according    to any of (1) to (7), wherein the thermoplastic elastomer (a) in the    adhesive layer (B) contains a styrene-butadiene block copolymer    and/or a styrene-isoprene block copolymer.-   (9) The photosensitive structure for flexographic printing according    to any of (1) to (8), wherein the adhesive layer (B) is partially or    completely polymerized by heat energy and/or light energy.-   (10) The photosensitive structure for flexographic printing    according to any of (1) to (9), wherein the adhesive layer (B)    contains a recovered photosensitive resin composition.-   (11) The photosensitive structure for flexographic printing    according to any of (1) to (10), wherein the support (A) has at    least one undercoat layer on the surface of the side on which the    adhesive layer (B) is laminated.-   (12) The photosensitive structure for flexographic printing    according to any of (1) to (11), wherein the support (A) has at    least one undercoat layer, and the undercoat layer contains at least    one selected from a group consisting of a composition containing a    (meth)acrylate polymer or a copolymer thereof as the major    component, a composition containing an aromatic polyurethane resin,    obtained from a polyisocyanate containing an aromatic ring and a    polyol, as the major component, and a composition containing the    both as the major component.-   (13) A method for preparing a photosensitive structure for    flexographic printing formed by laminating a support (A), an    adhesive layer (B) and a photosensitive resin layer (C) different    from the adhesive layer (B), wherein the adhesive layer (B) contains    a thermoplastic elastomer (a) derived from at least one monovinyl    substituted aromatic hydrocarbon and a conjugated diene, at least    one ethylenically unsaturated compound (b) and at least one    polymerization initiator (c), wherein the ethylenically unsaturated    compound (b) contains at least one (meth)acrylate (i) having one or    more aromatic rings and/or one or more hydroxyl groups in the    molecule thereof; the method having sequentially laminating the    support (A), the adhesive layer (B) and the photosensitive resin    layer.(C).-   (14) The method according to (13), further having a step for    laminating an adhesive layer (B) partially or completely polymerized    by heat or light.-   (15) The method according to (13) or (14), wherein the support (A)    has at least one undercoat layer, and the undercoat layer contains    at least one selected from a group consisting of a composition    containing a (meth)acrylate polymer or a copolymer thereof as the    major component, a composition containing an aromatic polyurethane    resin obtained from a polyisocyanate containing an aromatic ring and    a polyol, as the major component, and a composition containing the    both as the major component.-   (16) A support base material for a photosensitive structure for    flexographic printing formed by providing an adhesive layer (B) on a    support (A), wherein the adhesive layer (B) contains a thermoplastic    elastomer (a) derived from at least one monovinyl substituted    aromatic hydrocarbon and a conjugated diene, at least one    ethylenically unsaturated compound (b) and at least one    polymerization initiator (c), wherein the ethylenically unsaturated    compound (b) contains at least one (meth)acrylate (i) having one or    more aromatic rings and/or one or more hydroxyl groups in the    molecule thereof.-   (17) The support base material according to (16), wherein the    adhesive layer (B) is partially or completely polymerized by heat    energy and/or light energy.-   (18) The support base material according to (16) or (17), wherein    the support (A) has at least one undercoat layer on the surface of    the side on which the adhesive layer (B) is laminated.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be specifically described below primarilyreferring to the preferable embodiments thereof.

As a support (A) used in the present invention, known supports can beused, and for example, a polyester film, a polyamide sheet, a metalplate or the like can be used. Preferably, a dimensionally stablepolyester film having a thickness within a range between 75 and 300 μmis used. The examples of such polyester films include any aromaticpolyester film, such as a polyethylene terephthalate film, apolybutylene terephthalate film, and a polyethylene naphthalate film. Inorder to obtain a higher adhesive strength between an adhesive layer anda polyester film support, it is more preferable to form at least oneundercoat layer.

A polyester film has a layer applied to improve adhesiveness (undercoatlayer), and the undercoat layer is normally applied to have a thicknessof 0.001 to 1 μm. A polyester film having an undercoat layer ispreferably manufactured by applying undercoat layer components onto thefilm continuously with the step for manufacturing a biaxially-orientedfilm.

The presence of the undercoat layer can be checked by known techniques,such as infrared absorption spectrometry and electron spectroscopy.Also, the presence of the undercoat layer can be checked by radiatingion beams onto the support to decompose the surface of the support, andanalyzing the decomposition product.

Such films having undercoat layers are commercially available, and canbe used also in the present invention. The examples of such polyesterfilms having undercoat layers include “Lumirror T90” (trademark) seriesmanufactured by Toray Industries, Inc., “Cosmo Shine A4000” (trademark)series manufactured by Toyobo Co., Ltd., “Tetron HPE, SG2” (trademark)manufactured by Teijin Limited, and “Melinex 700” (trademark) seriesmanufactured by Du Pont KK.

From the point of view to obtain better adhesion, the major componentthat constitutes an undercoat layer is preferably a polymer of a(meth)acrylate. For example, the polymers or copolymers ofmethyl(meth)acrylate, ethyl(meth)acrylate, butyl(meth)acrylate,2-ethylhexyl (meth)acrylate, or glycidyl (meth)acrylate can be used. Asrequired, these (co)polymers can be used after copolymerizing with(meth)acrylic acid, styrene, acrylonitrile, or vinyl chloride.

Other components of the undercoat layer have preferably urethane bonds,and more preferably urethane bonds derived from an isocyanate compoundhaving one or more aromatic rings. The examples of such compoundsinclude a reaction product of a compound having active hydrogens and acompound having isocyanate groups. The examples of activehydrogen-containing compounds include diols, such as ethylene glycol,1,4-butane diol, neopentyl glycol, and polyether diols thereof.Polyester compounds can also form urethane bonds since they may haveactive hydrogens. The examples of dicarboxylic acid components inpolyester compounds include terephthalic acid and isophthalic acid; andthe examples of alcohol components include ethylene glycol, 1,4-butanediol, and polyether polyol compounds thereof. Condensation products ofthese dicarboxylic acid components and alcohol components (diols,polyols) can be used. The examples of polyisocyanates include aromaticisocyanates, such as toluene diisocyanate and 4,4-diphenylene methanediisocyanate.

An adhesive layer (B) used in the present invention must be an adhesivelayer (B) containing a thermoplastic elastomer (a) derived from at leastone monovinyl substituted aromatic hydrocarbon and a conjugated diene,at least one ethylenically unsaturated compound (b) and at least onepolymerization initiator (c), and the ethylenically unsaturated compound(b) has at least one (meth)acrylate (i) having one or more aromaticrings and/or one or more hydroxyl groups in the molecule thereof.

As the thermoplastic elastomer (a), commonly used polymers of amonovinyl substituted aromatic hydrocarbon and a conjugated dienemonomer can be used. The examples of the monovinyl substituted aromatichydrocarbon monomers include styrene, α-methylstyrene, p-methylstyrene,and p-methoxystyrene; and the examples of the conjugated diene monomersinclude butadiene and isoprene. The examples of the thermoplasticelastomers (a) include styrene-butadiene block copolymer andstyrene-isoprene block copolymer. As the thermoplastic elastomer (a),these block copolymers can be used alone, or can be used in combination.

From the point of view of adhesive strength, the content of thethermoplastic elastomer (a) in the adhesive layer is preferably 20% byweight or more, more preferably 30% by weight or more, and furtherpreferably 40% by weight or more.

The content of the ethylenically unsaturated compound (b) in theadhesive layer (B) is 1 to 20% by weight, preferably 1 to 15% by weightto the adhesive layer (B). The molecular weight of the ethylenicallyunsaturated compound (b) is lower than 5000, and more preferably 3000 orlower.

It is required that the ethylenically unsaturated compound (b) containsa (meth)acrylate (i) having an aromatic ring and/or a hydroxyl group ina molecule thereof.

The aromatic ring in the present invention is the generic term for ringsbelonging to aromatic series described in Encyclopedic Dictionary ofChemistry (published by Tokyo Kagaku Dojin Co., Ltd. in 1989). Thehydroxyl group used herein is a hydroxyl group also described inEncyclopedic Dictionary of Chemistry (published by Tokyo Kagaku DojinCo., Ltd. in 1989).

The examples of the (meth)acrylate that contains one or more aromaticrings include benzyl(meth)acrylate, phenoxyethyl(meth)acrylate,phenoxy-polyethylene glycol(meth)acrylate, an ester compound of benzoicacid, (meth)acrylic acid and another alcohol, and an addition product ofa (meth)acrylate and bisphenol A.

The examples of the (meth)acrylate having one or more hydroxyl groupsused in the present invention include 2-hydroxyethyl(meth)acrylate and2-hydroxypropyl(meth)acrylate.

The examples of the (meth)acrylate containing one or more aromatic ringsand/or one or more hydroxyl groups include2-hydroxy-3-phenoxypropyl(meth)acrylate, 2-(meth)acryloyloxyethylphthalate, 2-(meth)acryloyloxyethyl 2-hydroxyethyl phthalate,2-(meth)acryloyloxyethyl 2-hydroxypropyl phthalate, and an additionproduct of a glycidyl ether and (meth)acrylic acid.

From the point of view of adhesive strength, and of the resistance toink solvents and the stability in aging, it is preferable that(meth)acrylate (i) having an aromatic ring and/or a hydroxyl group in amolecule thereof has two or more ethylenically unsaturated groups.

Furthermore, from the point of view of adhesive strength, it ispreferable that (meth)acrylate (i) having an aromatic ring and/or ahydroxyl group in a molecule thereof has a bisphenol skeleton. Thebisphenol skeleton in the present invention means an aromatic dioxycompound as described in “Lecture of Plastic Material 5, PolycarbonateResins” (M. Matsugane, S. Tahara, S. Katoh, published by Nikkan KogyoShimbun, Ltd. in 1969. The skeleton can be obtained by synthesis fromthe compound represented by the following Formula (1), and is a skeletonrepresented by the following Formula (2).

wherein R′ and R″ represent hydrogen, an alkane (including cycloalkane)having 1 to 6 carbon atoms, or an aromatic ring having 6 to 12 carbonatoms; and X and Y represent an alkane (including cycloalkane) having 1to 12 carbon atoms, or a halogen.

wherein R′ and R″ represent hydrogen, an alkane (including cycloalkane)having 1 to 12 carbon atoms, or an aromatic ring having 6 to 12 carbonatoms; and X and Y represent an alkane (including cycloalkane) having 1to 6 carbon atoms, or a halogen.

The examples of such compounds having bisphenol skeletons include 2-molebisphenol A propylene oxide adduct diglycidyl ether(meth)acrylic acidadduct, bisphenol A ethylene oxide adduct di(meth)acrylate, bisphenol Adiglycidyl ether(meth)acrylic acid adduct, and bisphenol F ethyleneoxide modified di(meth)acrylate.

From the point of view of adhesive strength, it is preferable that theethylenically unsaturated compound (b) contains apolyester(meth)acrylate (ii) having two or more ethylenicallyunsaturated bonds in a molecule thereof. Such polyester(meth)acrylates,for example, 1,6-hexanediol di(meth)acrylate or 1,9-nonanedioldi(meth)acrylate can be used.

A combination of more than one polyester (meth)acrylate enables adhesivestrengths both between the adhesive layer and the support and betweenthe adhesive layer and the photosensitive resin layer to be dramaticallyimproved.

The weight ratio (i):(ii) of a polyester (meth)acrylate having two ormore ethylenically unsaturated bonds in a molecule thereof (i) and(meth)acrylate having an aromatic ring and/or a hydroxyl group in amolecule thereof (ii) is 0.01:1 to 10:1, preferably 0.01:1 to 8:1, andmore preferably 0.01:1 to 6:1.

From the point of view of adhesive strength, it is preferable that the(meth)acrylate (i) having an aromatic ring and/or a hydroxyl group in amolecule thereof has two or more ethylenically unsaturated groups. Inthis case, the characteristics of both (meth)acrylate having an aromaticring and/or a hydroxyl group in a molecule thereof (i) and apolyester(meth)acrylate having two or more ethylenically unsaturatedbonds in a molecule thereof (ii) can be satisfied. In addition, from thepoint of view of properties of the adhesive layer, even if(meth)acrylate having an aromatic ring and/or a hydroxyl group in amolecule thereof has two or more ethylenically unsaturated groups, it ispreferable to add an ethylenically unsaturated compound having two ormore ethylenically unsaturated groups but neither aromatic rings norhydroxyl groups.

The adhesive layer (B) must contain a polymerization initiator (c). Asthe polymerization initiator, a photopolymerization initiator or athermal polymerization initiator can be used. As the polymerizationinitiator, any known polymerization initiator can be used. From thepoint of view of productivity and handling, the use of aphotopolymerization initiator is preferable as the polymerizationinitiator.

As such a photopolymerization initiator, a photopolymerization initiatorcommonly used in a photosensitive resin composition can be used. As sucha photopolymerization initiator, for example, known radicalpolymerization initiator, such as aromatic ketones and benzoyl etherscan be used. For example, the radical polymerization initiator can beselected from benzophenone, Michler's ketone, benzoin methyl ether,benzoin ethyl ether, benzoin isopropyl ether, α-methylol benzoin methylether, and α-methoxy benzoin methyl ether,2,2-dimethoxyphenylacetophnone, and the combination thereof can also beused. From the point of view of sensitivity to ultraviolet rays, thecontent of the photopolymerization initiator to the total weight of theadhesive layer is preferably 0.1 to 10% by weight, and more preferably0.1 to 8% by weight.

In addition, a plasticizer, a sensitizer, a thermal polymerizationinhibitor, colorants, dyes, pigments, fillers or a hydrophilic copolymercan be added to the adhesive layer.

The photosensitive resin layer (C) used in the present invention must bedifferent from the adhesive layer (B). Even when the photosensitiveresin layer (C) contains a binder different from the thermoplasticelastomer (a) in the adhesive layer (B), or the contents thereof aredifferent from each other, the adhesive layer (B) is considered to bedifferent from the photosensitive resin layer (C). Furthermore, in thepresent invention, even if different ethylenically unsaturated compoundsor pyhotopolymerization initiators are used between the adhesive layer(B) and the photosensitive resin layer (C) as each component thereof, orthe added amounts of those components are different from each other, theadhesive layer (B) is deemed to be different from the photosensitiveresin layer (C). When the added amounts are different by 0.01% by weightor more, the compositions are deemed to be different. In addition, whenthe presence or absence, the type, or the added amount is different forthe plasticizer, sensitizer, thermal polymerization inhibitor,colorants, dyes, pigments, fillers or hydrophilic copolymer, which iscontained in the adhesive layer, the composition is deemed as adifferent composition.

The photosensitive resin layer (C) used in the present invention can bea known photosensitive resin composition.

From the point of view of printing quality and handling, as thephotosensitive resin composition used in the photosensitive resin layer,it is preferable that the photosensitive resin layer (C) is a mixture ofa thermoplastic elestomer composed of at least one monovinyl-substitutedaromatic hydrocarbon and a conjugated diene, at least one ethylenicallyunsaturated compound, and at least one photopolymerization initiator.

As a thermoplastic elastomer used in the present invention, a commonlyused polymer of a monovinyl-substituted aromatic hydrocarbon and aconjugated diene monomer can be used. The examples of themonovinyl-substituted aromatic hydrocarbons include styrene,α-methylstyrene, p-methylstyrene and p-methoxystyrene; and the examplesof the conjugated diene monomers include butadiene and isoprene. Thetypical examples of the thermoplastic elastomers include astyrene-butadiene block copolymer and a styrene-isoprene blockcopolymer.

In order to obtain mechanical properties required for a plate, athermoplastic elastomer having a molecular weight of 5,000 or more,preferably 10,000 or more, and more preferably 20,000 or more in thequantity of preferably 50% by weight or more, and more preferably 50 to85% by weight, on the basis of the total weight of the photosensitiveresin.

As the ethylenically unsaturated compound, a monomer commonly used inphotosensitive composition can be used. For example, an ester of analcohol, such as t-butyl alcohol and lauryl alcohol, and acrylic acid; amaleimide derivative, such as lauryl maleimide, cyclohexyl maleimide,and benzyl maleimide; a fumaric acid ester, such as dioctyl fumarate;and an ester of a polyvalent alcohol and acrylic acid or methacrylicacid, such as hexanediol(meth)acrylate, nonanediol(meth)acrylate, andtrimethylol(meth)acrylate can be used alone or in combination in thephotosensitive resin.

Since the quantity of the ethylenically unsaturated compound relates tothe reactivity of the photosensitive resin to ultraviolet rays, thequantity is 1 to 20% by weight, and preferably 1 to 15% by weight on thebasis of the total weight of the photosensitive resin. The molecularweight of the ethylenically unsaturated compound is preferably lowerthan 5,000, and more preferably 3,000 or lower.

As the photopolymerization initiator, a heretofore radicalpolymerization initiator, such as aromatic ketones and benzoyl ethers,can be used. For example, the radical polymerization initiator can beselected from benzophenone, Michler's ketone, benzoin methyl ether,benzoin ethyl ether, benzoin isopropyl ether, α-methylol benzoin methylether, and α-methoxy benzoin methyl ether,2,2-dimethoxyphenylacetophnone, and the combination thereof can also beused.

From the point of view of sensitivity to ultraviolet rays, the contentof the photopolymerization initiator to the total weight of the adhesivelayer is preferably 0.1 to 10% by weight, and more preferably 0.1 to 8%by weight.

In addition, a plasticizer, a sensitizer, a thermal polymerizationinhibitor, colorants, dyes, fillers or a hydrophilic copolymer can beadded to the adhesive layer.

The above-described photosensitive resin composition can also be used asa component of the adhesive layer. When the (meth)acrylate having one ormore aromatic rings and/or one or more hydroxyl groups in a moleculethereof (i) is contained in the photosensitive resin composition as anethylenically unsaturated compound (b), the photosensitive resincomposition can be used as the adhesive layer; and when it is notcontained, by adding the (meth)acrylate having one or more aromaticrings and/or one or more hydroxyl groups in a molecule thereof (i), theadhesive layer can be formed. For the photosensitive resin layer used inthis case, for example, a rejected plate product that may be produced inthe manufacturing step can be used, and in such a case, the rejectedplate product can be preferably recycled.

The recovery in the present invention means the reuse of rejected plateproduct that may be produced in the manufacturing step. The recoveredphotosensitive resin means a reused photosensitive resin when aphotosensitive resin composition prepared as a photosensitive resinlayer is reused at least once.

The adhesive layer (B) and the photosensitive resin layer (C) of thepresent invention can be prepared by various methods. For example, thesecan be obtained, for example, by dissolving and mixing a thermoplasticelastomer, an ethylenically unsaturated compound, a photopolymerizationinitiator and the like in a suitable solvent, such as chloroform andtoluene, casting them in a mold form, and evaporating the solvent.Furthermore, these can be kneaded using a kneader or a roll, and formedto a desired thickness using an extruder, an injection molding machineor a press. By sequentially laminating the support (A), the adhesivelayer (B) and the photosensitive resin layer (C), a photosensitivestructure can be obtained.

Alternatively, a photosensitive structure can also be obtained bylaminating the adhesive layer (B) on the support (A), and bonding thesupport (A) having the adhesive layer (B) with the photosensitive resinlayer (C).

The adhesive layer (B) can also be prepared by dissolving athermoplastic elastomer (a), an ethylenically unsaturated compound (b),and a photopolymerization initiator (c) in a suitable solvent, such astoluene and ethyl acetate, and then coating the support (A) with thesolution. For coating, known methods can be used, and for example, a barcoater, a gravure coater or the like can be used.

When the adhesive layer (B) is bonded to the photosensitive resin layer(C) after laminating the adhesive layer (B) on the support (A), it ispreferable to partially or completely polymerize the adhesive layer (B)from the point of view of adhesive strength. From the point of view ofproduction efficiency, the method for polymerization is preferablyphotopolymerization, and the method and time for photopolymerization isnot specifically limited. For example, after ultraviolet rays areradiated onto the support (A) to which the adhesive layer (B) is appliedto perform polymerization reaction, the support (A) can be bonded to thephotosensitive resin layer (C). Alternatively, after bonding the support(A) to which the adhesive layer (B) is applied to the photosensitiveresin layer (C), ultraviolet rays can be radiated to causepolymerization.

The presence of polymerization reaction can be checked by change insolubility of the photosensitive structure for flexographic printing ina developer solvent, such as toluene and tetrachloroethylene. Forexample, if the adhesive layer (B) is not completely or partiallydissolved when a partially or completely polymerized adhesive layer (B)is immersed in the above-described solvent, it is judged thatpolymerization reaction has occurred.

Furthermore, even when the adhesive layer is completely dissolved, thepresence of polymerization reaction can be checked by measuring themolecule weight distribution of the adhesive layer. As the means formeasuring molecule weight distribution, known analyzing techniques canbe used. For example, the presence of polymerization reaction can bechecked by measuring the molecule weight before and after thepolymerization reaction using GPC (gel permeation chromatography).

From the adhesive layer after polymerization, the composition of theadhesive layer before polymerization can be checked. In this case, thecomposition of the adhesive layer before polymerization can be checkedusing known analyzing techniques.

By measuring the infrared absorption spectra of the polymerizedadhesive, the composition of the adhesive layer can be checked. Thepresence of an ethylenically unsaturated compound that has notpolymerized or a polymerization initiator can be checked by testing thepolymerized adhesive layer using thermal decomposition gaschromatography. The presence of the initiator before polymerization canalso be determined from the decomposition products of the polymerizationinitiator detected during the thermal decomposition gas chromatography.

In addition, the composition of the adhesive before polymerization canbe checked by immersing the polymerized adhesive layer in a solvent suchas chloroform to extract the ethylenically unsaturated compound that hasnot reacted, the polymerization initiator and the decomposition productsthereof, and testing the extracts using an NMR method or a gaschromatography method.

Furthermore, the composition of the adhesive before polymerization canalso be checked by radiating ion beams onto the adhesive layer todecompose the adhesive composition, and testing the decompositionproducts thereof.

The thickness of the adhesive layer (B) is 0.0001 to 1 mm, preferably0.001 to 1 mm, and more preferably 0.001 to 0.5 mm.

In the support base of the present invention, an adhesive layer (B) islaminated on a support (A), and the adhesive layer (B) contains athermoplastic elastomer (a) formed of at least one monovinyl-substitutedaromatic hydrocarbon and a conjugated diene, at least one ethylenicallyunsaturated compound (b), and at least one polymerization initiator (c);and the adhesive layer having the ethylenically unsaturated compound (b)that contains at least one (meth)acrylate (i) having one or morearomatic rings and/or one or more hydroxyl groups in a molecule thereofis laminated on the support. The above-described adhesive layer (B) canbe laminated on the support (A) using the above-described method.

The adhesive layer of the support base can be used after partially orcompletely polymerizing, but when polymerization reaction is performed,polymerization by photoreaction is preferable from the point of view ofproduction efficiency. When the adhesive layer of the support base ispolymerized by photoreaction, the light can be radiated from the supportside, specifically in the manner that the light passes through thesupport; or the light can be radiated from the adhesive side,specifically without passing through the support. The presence ofpolymerization reaction can be checked by the above-described methods.

Since the photosensitive resin layer may have tackiness depending on thecomposition, a thin flexible protective film that is soluble in thedeveloper solution can be formed in order to improve the contact with atransparent image carrier overlaid on the photosensitive resin layer inplate making, or to enable the reuse of the transparent image carrier.For example, a thin film soluble in the developer solution consisting ofpolyimide, alkyl cellulose, hydroxyalkyl cellulose, nitro cellulose,cellulose ester, copolymers of a monovinyl-substituted aromatichydrocarbon and a conjugated diene, the hydrogenating reaction productsof copolymers of a monovinyl-substituted aromatic hydrocarbon and aconjugated diene (for example, refer to JP-A-2002-268228) can be used.

A flexographic plate can be obtained by processing the above-describedphotosensitive structure for flexographic printing using an ordinaryplate making method. The examples of an ultraviolet exposure source foroptically curing the photosensitive resin used in the plate-makingprocess include high-voltage mercury lamps, ultraviolet fluorescentlamps, carbon arc lamps and xenon lamps. By exposing a photosensitiveresin to ultraviolet rays through a transparent image carrier, a desiredimage can be obtained. In order to strengthen the adhesion of thesupport to the photosensitive resin layer, furthermore, in order tostabilize the relief image against stress produced when washing theunexposed portions, flood exposure from the support side is effective.The exposure from the transparent image carrier side and the exposurefrom the support side can be performed in an optional order, also can beperformed simultaneously. From the point of view of imagereproducibility, it is preferable to perform the exposure from thesupport side first.

The examples of developer solvents used for washing the unexposedportions include chlorine-based solvents, such as 1,1,1-trichloroethaneand tetrachloroethylene; esters, such as heptyl acetate and3-methoxybutyl acetate; hydrocarbons such as petroleum distillate,toluene and decalin; and the mixtures of these solvents to whichalcohols, such as propanol and butanol, are added. The washing of theunexposed portions is performed by injecting the solvent from a nozzle,of brushing using a brush. The obtained plate is cleaned by rinsing, andafter drying, post exposure is performed to complete a plate.

Furthermore, a plate for laser engraving to form patterns can befabricated by forming a layer that can be laser-engraved cured byradiating ultraviolet rays onto the entire surface of the photosensitiveresin layer, and thereafter, radiating laser beams, and removing theresin in the portion exposed to the beams.

The present invention will be described in more detail on the basis ofexamples; however, the technical scope of the present invention is notlimited to these examples.

Relating to compositions described below, parts by weight will be usedunless otherwise specified.

EXAMPLES Example 1

(1) Preparation of a Photosensitive Resin Layer

Photosensitive resin composition having the compositions shown in Table1 were kneaded using a kneader to form photosensitive resin compositions1 and 2. Each resultant photosensitive resin composition was sandwichedbetween a siliconized polyester film and a polyethylene terephthalatefilm having a polyamide film, and pressed using a 3-mm spacer underconditions of a temperature of 130° C. and a pressure of 1.96×10⁷ Pa for4 minutes. The thickness of the obtained photosensitive resin layer was3.0 mm.

(2) Preparation of an Adhesive Layer

As an adhesive layer, 55 parts of styrene-butadiene copolymer (trademark“Toughprene 912”, manufactured by Asahi Kasei corporation), 38 parts ofparaffin oil (average carbon number: 33, average molecular weight: 470,density at 15° C.: 0.868), 2.5 parts of 1,9-nonanediol diacrylate, 1.5parts of 2,2-dimethoxy-phenyl acetophenone, and 3 parts of Monomer 1described in Table 2 were dissolved in toluene to form a solution of asolid content of 25%. The solution was applied onto polyester film so asto have a thickness of 100 μm using a knife coater to form an adhesivelayer.

(3) Preparation of a Photosensitive Structure for Flexographic Printing

The siliconized polyethylene terephthalate film was peeled from thephotosensitive resin layer and placed on a stainless steel plate heatedto 130° C. to heat each layer consisting of photosensitive resins 1 and2, respectively. The adhesive layer is laminated on the heatedphotosensitive resin layer so as to contact the photosensitive resinlayer to fabricate a photosensitive structure.

(4) Fabrication of a Flexographic Plate and Evaluation of its AdhesiveStrength

The obtained photosensitive structure was placed on “AFP-1500”(trademark, manufactured by Asahi Kasei Corporation), and image exposureof 6,000 mJ/cm² was performed through a transparent image carrier usingan ultraviolet fluorescent lamp having a center wavelength at 370 nm. Atthis time, the exposure intensity was measured by a UV illuminance meter“MO-2” (trademark) manufactured by Orc, Inc. using a UV-35 filter. Then,the photosensitive structure was developed using “AFP-1500” developingmachine (manufactured by Asahi Kasei Corporation) using a developersolution composed of tetrachloroethylene and n-butanol in a volume ratioof 3/1, dried at 60° C. for 1 hour, and undergone post exposure toobtain a flexographic plate.

In order to measure the peeling strength of the support and thephotosensitive resin in the obtained flexographic plate, when thesupport was forcibly peeled from the sample prepared by cutting thecured resin layer into 1-cm rectangle, and the resin layer was peeledfrom the support using a tensile tester at an angle of 180° and a speedof 50 mm/min, the result shown in Table 3 was obtained. As Table 3shows, a strength of 5.9 N/cm was obtained from both the photosensitiveresins 1 and 2.

When printing was performed on a polyethylene film using the obtainedflexographic plate with an ink containing about 15% by weight of anacetic acid ester, the cured resin was not peeled from the support dueto shear stress of the plate cylinder and the impression cylinder, andfurthermore, even if a large force to peel the portion of the curedresin layer by hand was applied to the cured resin layer in order toremove the plate fixed by a double-sided adhesive tape after printing,the plate did not break, and adhered tightly to the support.

In addition, when the sides of the removed flexographic plate afterprinting were observed, it was found that the adhesive layer was notdissolved in the solvent of the used ink, and had resistance to inksolvents.

When adhesive strength was measured after the plate after printing wasaged under a condition of 20° C. for 14 days, a high adhesive strengthwas maintained in both photosensitive resins 1 and 2 as shown in Table3.

Example 2

(1) Preparation of a Photosensitive Resin

In the same manner as in Example 1, each photosensitive resin layercomposed of photosensitive resin composition 1 or 2, respectively, wasprepared.

(2) Preparation of a Polyester Film

After the condensation reaction of 93 g of ethylene glycol, 374 g ofneopentyl glycol, and 382 g of phthalic acid in an atmospheric ambienceat a reaction temperature of 180° C. under a reduced pressure of1.33×10³ Pa for 6 hours, 125 g of 4,4-diphennylene diisocyanate wasadded, and further allowed to react at 80° C. for 5 hours. The resultedresin was dissolved in water to form a 10% aqueous solution, thesolution was applied onto a melt-extruded polyethylene terephthalatefilm, and the film was biaxially oriented to obtain a polyester filmhaving an undercoat layer. The thickness of the obtained undercoat layerwas 0.05 μm.

(3) Preparation of an Adhesive Layer

As an adhesive layer, 55 parts of a styrene-butadiene copolymer(“Toughprene 912”, trademark, manufactured by Asahi Kasei Corporation),38 parts of paraffin oil (average carbon number: 33, average molecularweight: 470, density at 15° C.: 0.868), 2.5 parts of 1,9-nonanedioldiacrylate, 1.5 parts of 2,2-dimethoxy-phenyl acetophenone, and 3 partsof Monomer 2 shown in Table 2 were dissolved in toluene to form asolution having 25% solid content. The solution was applied onto thepolyester film obtained in (2) to a thickness of 25 μm using a knifecoater to form an adhesive layer.

(4) Preparation of a Photosensitive Resin Structure

In the same manner as in Example 1, a photosensitive resin structure wasprepared. Furthermore, in the same manner as in Example 1, samples foraging evaluation were also prepared.

(5) Fabrication of Flexographic Plate and Evaluation of AdhesiveStrength

In the same manner as in Example 1, the plate-making process was carriedout, and the adhesive strength was measured. As a result of measurement,as shown in Table 3, both photosensitive resin compositions 1 and 2exhibited a favorable adhesive strength regardless of whether aging wasperformed or not. Furthermore, in the same manner as in Example 1,peeling tests by printing were also conducted, but the samples exhibiteda favorable adhesive strength without being peeled off.

In addition, when the sides of the removed flexographic plate afterprinting were observed, it was found that the adhesive layer was notdissolved in the solvent of the used ink, and had resistance to inksolvents.

When adhesive strength was measured after the plate after printing wasaged under a condition of 20° C. for 14 days, a high adhesive strengthwas maintained in both photosensitive resins 1 and 2 as shown in Table3.

Example 3

(1) Preparation of a Photosensitive Resin

In the same manner as in Example 1, each photosensitive resin layercomposed of photosensitive resin composition 1 or 2, respectively, wasprepared.

(2) Preparation of a Polyester Film

A polyester film having an undercoat layer was prepared in the samemanner as in Example 2.

(3) Preparation of an Adhesive Layer

As an adhesive layer, 18 parts of a styrene-butadiene copolymer(“Toughprene 912”, trademark, manufactured by Asahi Kasei Corporation),37 parts of styrene-isoprene copolymer (“KRATON D1112”, trademark,manufactured by Kraton Polymers Japan, Ltd.), 38 parts of paraffin oil(average carbon number: 33, average molecular weight: 470, density at15° C.: 0.868), 2.5 parts of 1,9-nonanediol diacrylate, 1.5 parts of2,2-dimethoxy-phenyl acetophenone, and 3 parts of Monomer 1 shown inTable 2 were dissolved in toluene to form a solution having 25% solidcontent. The solution was applied onto the polyester film obtained in(2) to a thickness of 25 μm using a knife coater to form an adhesivelayer.

A siliconized polyester film was bonded so as to contact the obtainedadhesive layer, and an exposure of 50 mJ/cm² of the obtained supporthaving an adhesive layer was performed on “AFP-1500” (trade mark,manufactured by Asahi Kasei Corporation) through a transparent imagecarrier using an ultraviolet fluorescent lamp having a center wavelengthat 370 nm. At this time, the exposure intensity was measured by a UVilluminance meter “MO-2” (trademark) manufactured by Orc, Inc. using aUV-35 filter.

(4) Preparation of a Photosensitive Resin Structure

In the same manner as in Example 1, the siliconized polyester film waspeeled from the photosensitive resin layer and the adhesive layer, andbonded so that the layers contact to each other to form a photosensitiveresin structure. Also in the same manner as in Example 1, samples foraging evaluation were also prepared.

(5) Fabrication of a Flexographic Plate and Evaluation of its AdhesiveStrength

In the same manner as in Example 1, the plate-making process was carriedout, and the adhesive strength was measured. As a result of measurement,as shown in Table 3, both photosensitive resin compositions 1 and 2exhibited a favorable adhesive strength. Furthermore, in the same manneras in Example 1, peeling tests by printing were also conducted, but thesamples exhibited a favorable adhesive strength without being peeledoff.

In addition, when the sides of the removed flexographic plate afterprinting were observed, it was found that the adhesive layer was notdissolved in the solvent of the used ink, and had resistance to inksolvents.

When adhesive strength was measured after the plate after printing wasaged under a condition of 20° C. for 14 days, a high adhesive strengthwas maintained in both photosensitive resins 1 and 2 as shown in Table3.

Example 4

(1) Preparation of a Photosensitive Resin

In the same manner as in Example 1, each photosensitive resin layercomposed of photosensitive resin composition 1 or 2, respectively, wasprepared.

(2) Preparation of a Polyester Film

A polyester film having an undercoat layer was prepared in the samemanner as in Example 2.

(3) Preparation of an Adhesive Layer

As an adhesive layer, 22 parts of a styrene-butadiene copolymer(“Toughprene 912”, trademark, manufactured by Asahi Kasei Corporation),33 parts of styrene-isoprene copolymer (“KRATON D1112”, trademark,manufactured by Kraton Polymers Japan, Ltd.), 38 parts of paraffin oil(average carbon number: 33, average molecular weight: 470, density at15° C.: 0.868), 2.5 parts of 1,9-nonanediol diacrylate, 1.5 parts of2,2-dimethoxy-phenyl acetophenone, and 3 parts of Monomer 3 shown inTable 2 were dissolved in toluene to form a solution having 25% solidcontent. The solution was applied onto the polyester film obtained in(2) to a thickness of 25 μm using a knife coater to form an adhesivelayer.

(4) Preparation of a Photosensitive Resin Structure

In the same manner as in Exaple 1, a photosensitive resin structure wasrepared.

(5) Fabrication of Flexographic Plate and Evaluation of AdhesiveStrength

In the same manner as in Example 1, the plate-making process was carriedout, and the adhesive strength was measured. As a result of measurement,as shown in Table 3, both photosensitive resin compositions 1 and 2exhibited a favorable adhesive strength. Furthermore, in the same manneras in Example 1, peeling tests by printing were also conducted, but thesamples exhibited a favorable adhesive strength without being peeledoff.

In addition, when the sides of the removed flexographic plate afterprinting were observed, it was found that the adhesive layer was notdissolved in the solvent of the used ink, and had resistance to inksolvents.

When adhesive strength was measured after the plate after printing wasaged under a condition of 20° C. for 14 days, a high adhesive strengthwas maintained in both photosensitive resins 1 and 2 as shown in Table3.

Example 5

(1) Preparation of a Photosensitive Resin

In the same manner as in Example 1, each photosensitive resin layercomposed of photosensitive resin composition 1 or 2, respectively, wasprepared.

(2) Preparation of a Polyester Film

A polyester film having an undercoat layer was prepared in the samemanner as in Example 2.

(3) Preparation of Adhesive Layer

Ninety four parts of the photosensitive resin composition 1 obtained inExample 1, 3 parts of hexamethylene dimethacrylate, and 3 parts ofMonomer 1 shown in Table 2 were dissolved in toluene to form a solutionhaving 25% solid content.

The solution was applied onto a polyester film in the same manner as inExample 2 to form an adhesive layer having a thickness of 25 μm.Exposure of 50 mJ/cm² of the adhesive layer was performed in the samemanner as in Example 3.

(4) Preparation of a Photosensitive Resin Structure

In the same manner as in Exaple 1, a photosensitive resin structure wasrepared.

(5) Fabrication of a Flexographic Plate and Evaluation of its AdhesiveStrength

In the same manner as in Example 1, the plate-making process was carriedout, and the adhesive strength was measured. As a result of measurement,as shown in Table 3, both photosensitive resin compositions 1 and 2exhibited a favorable adhesive strength. Furthermore, in the same manneras in Example 1, peeling tests by printing were also conducted, but thesamples exhibited a favorable adhesive strength without being peeledoff.

In addition, when the sides of the removed flexographic plate afterprinting were observed, it was found that the adhesive layer was notdissolved in the solvent of the used ink, and had resistance to inksolvents.

When adhesive strength was measured after the plate after printing wasaged under a condition of 20° C. for 14 days, a high adhesive strengthwas maintained in both photosensitive resins 1 and 2 as shown in Table3.

Example 6

(1) Preparation of a Photosensitive Resin

In the same manner as in Example 1, each photosensitive resin layercomposed of photosensitive resin composition 1 or 2, respectively, wasprepared.

(2) Preparation of a Polyester Film

A polyester film having an undercoat layer was prepared in the samemanner as in Example 2.

(3) Preparation of an Adhesive Layer

As an adhesive layer, 55 parts of a styrene-butadiene copolymer(“Toughprene 912”, trademark, manufactured by Asahi Kasei Corporation),38 parts of paraffin oil (average carbon number: 33, average molecularweight: 470, density at 15° C.: 0.868), 2.5 parts of 1,9-nonanedioldiacrylate, 1.5 parts of 2,2-dimethoxy-phenyl acetophenone, and 3 partsof Monomer 4 shown in Table 2 were dissolved in toluene to form asolution having 25% solid content. The solution was applied onto thepolyester film obtained in (2) to a thickness of 25 μm using a knifecoater to form an adhesive layer.

(4) Preparation of a Photosensitive Resin Structure

In the same manner as in Exaple 1, a photosensitive resin structure wasrepared.

(5) Fabrication of a Flexographic Plate and Evaluation of its AdhesiveStrength

In the same manner as in Example 1, the plate-making process was carriedout, and the adhesive strength was measured. As a result of measurement,as shown in Table 3, although both photosensitive resin compositions 1and 2 exhibited a favorable adhesive strength, unevenness in adhesivestrength was observed. However, in the same manner as in Example 1,peeling tests by printing were also conducted, but the samples exhibiteda favorable adhesive strength without being peeled off.

In addition, when the sides of the removed flexographic plate afterprinting were observed, it was found that the adhesive layer wasdissolved in the solvent of the used ink although slightly.

When adhesive strength was measured after the plate after printing wasaged under a condition of 20° C. for 14 days, a high adhesive strengthof both photosensitive resins 1 and 2 was lower than 5.9 N/cm as shownin Table 3.

Comparative Example 1

(1) Preparation of a Photosensitive Resin

In the same manner as in Example 1, each photosensitive resin layercomposed of photosensitive resin composition 1 or 2, respectively, wasprepared.

(2) Preparation of an Adhesive Layer

After the condensation reaction of 624 g of neopentyl glycol, 93 g ofethylene glycol, sebacic acid and 382 g of phthalic acid in anatmospheric ambience at a reaction temperature of 180° C. under areduced pressure of 1330 Pa for 6 hours, 87 g of trimethylenediisocyanate was added, and further allowed to react for 5 hours. To 15parts of the resulted polyol, 1 part of xylene isocyanate was added, anddissolved in ethyl acetate to form a uniform solution, which was appliedonto a polyester film in the same manner as in Example 1 to prepare asupport having an adhesive layer.

(3) Preparation of a Photosensitive Resin Structure

A photosensitive-resin structure was prepared in the same manner as inExample 1.

(4) Fabrication of a Flexographic Plate and Evaluation of its AdhesiveStrength

A plate-making process was carried out in the same manner as in Example1, and adhesive strength was measured. As a result of measurement, asTable 3 shows, although favorable adhesive strength was obtained by thephotosensitive resin composition 1, the adhesive strength wasinsufficient in the photosensitive resin layer 2.

Furthermore, when a printing test was conducted in the same manner as inExample 1 and the adhesive strength was measured, the photosensitiveresin 1 exhibited a favorable adhesive strength without being peeledoff. On the other hand, in the case of the photosensitive resin 2, whenthe flexographic plate was peeled from the support after printing, thedetachment of the photosensitive resin layer from the support occurred.For the photosensitive resin 1, when aging was performed in the samemanner as in Example 1 to evaluate the adhesive strength, a favorableadhesive strength was exhibited also after aging.

For the photosensitive resin 2, since it was peeled from thephotosensitive resin layer when the flexographic plate was peeled fromthe plate cylinder, no samples for the aging test could be obtained toevaluate aging.

When the sides of the removed flexographic plate of the photosensitiveresin 1 after printing were observed, it was found that the adhesivelayer was not dissolved in the solvent of the used ink, and hadresistance to ink solvents.

For the photosensitive resin 2, since the photosensitive resin waspeeled off when the plate was removed from the plate cylinder, theadhesive layer became unclear, and therefore resistance to ink solventsremained unknown.

Comparative Example 2

(1) Preparation of Photosensitive Resin

In the same manner as in Example 1, each photosensitive resin layercomposed of photosensitive resin composition 1 or 2, respectively, wasprepared.

(2) Preparation of Adhesive Layer

An adhesive layer was prepared in the same manner as in Example 1 exceptthat the Monomer 1 was excluded from the adhesive layer of Example 1.

(3) Preparation of a Photosensitive Resin Structure

A photosensitive resin structure was prepared in the same manner as inExample 1.

(4) Fabrication of a Flexographic Plate and Evaluation of its AdhesiveStrength

A plate-making process was carried out in the same manner as in Example1, and adhesive strength was measured. As a result of measurement, asTable 3 shows, both photosensitive-resin compositions 1 and 2 hadinsufficient adhesive strength.

Furthermore, when a printing test was conducted in the same manner as inExample 1 and the adhesive strength was measured, detachment of thephotosensitive resin layer from the support occurred for bothphotosensitive resins 1 and 2 when the flexographic plate was peeledfrom the plate cylinder.

For both photosensitive resins 1 and 2, since the photosensitive resinlayer was detached when the flexographic plate was peeled from the platecylinder, no samples for the aging test could be obtained to evaluateaging.

Since both photosensitive resins 1 and 2 were detached when the platederived from each of them was removed from the plate cylinder, theadhesive layer became unclear, and therefore resistance to ink solventsremained unknown.

Comparative Example 3

(1) Preparation of a Photosensitive Resin

In the same manner as in Example 1, each photosensitive resin layercomposed of photosensitive resin composition 1 or 2, respectively, wasprepared.

(2) Preparation of Adhesive Layer

Ninety parts of a thermoplastic polyamide (“Macromelt 6900”, trademark,manufactured by Henkel Japan Corporation), 4 parts of 1,9-nonanedioldiacrylate, 2 parts of 2,2-dimethoxy-phenyl acetone, and 4 parts of theMonomer 4 shown in Table 2 were dissolved in a 1:1 (ratio by weight)mixed solution of toluene and isopropyl alcohol to form a solutionhaving a concentration by weight of 25%.

Using this solution, in the same manner as in Example 1, an adhesivelayer of a thickness of 25 μm was formed on a polyester film.Ultraviolet rays of 50 mJ/cm² were radiated onto the polyester film inthe same manner as in Example 3.

(3) Preparation of a Photosensitive Resin Structure

In the same manner as in Example 1, a photosensitive resin structure wasprepared.

(4) Fabrication of a Flexographic Plate and Evaluation of its AdhesiveStrength

A plate-making process was carried out in the same manner as in Example1, and adhesive strength was measured. As a result of measurement, asTable 3 shows, both photosensitive resin compositions 1 and 2 hadinsufficient adhesive strength.

Furthermore, when a printing test was conducted in the same manner as inExample 1 and the adhesive strength was measured, detachment of thephotosensitive resin layer from the support occurred for bothphotosensitive resins 1 and 2 when the flexographic plate was peeledfrom the plate cylinder.

For both photosensitive resins 1 and 2, since the photosensitive resinlayer was detached when the flexographic plate was peeled from the platecylinder, no samples for the aging test could be obtained to evaluateaging.

Since both photosensitive resins 1 and 2 were detached when the platederived from each of them was removed from the plate cylinder, theadhesive layer became unclear, and therefore resistance to ink solventsremained unknown.

TABLE 1 Photosensitive Photosensitive Components of photosensitive resin1 (part resin 2 resin composition by weight) (part by weight) ToughpreneA 60 60 (styrene-butadiene block copolymer from Asahi Kasei Corporation)B-2000 (liquid polybutadiene from 30 30 Nippon Petrochemicals Co., Ltd.)1,9-Nonanediol diacrylate 7 Dioctyl fumarate 5 Lauryl maleimide 22,2-Dimethoxy-phenyl acetophenone 2 2 2,6-di-t-butyl-p-cresol 1 1

TABLE 2 Chemical formula Monomer 1

Monomer 2

Monomer 3

Monomer 4

TABLE 3 Adhesiveness to Adhesiveness to Adhesiveness to Adhesiveness tophotosensitive photosensitive photosensitive photosensitive resin 1resin 1 after aging*¹ resin 2 resin 2 after aging*¹ (N/cm) (N/cm) (N/cm)(N/cm) Example 1 5.9 6.0 5.9 5.9 Example 2 9.8 9.7 9.8 9.8 Example 314.7 14.2 11.8 11.6 Example 4 No detachment No detachment 11.8 11.8Example 5 7.8 7.9 7.8 7.8 Example 6 9.8, 5.9*² 3.9 9.8, 6.2*² 4.0Comparative 10.8 10.8 1.0 Cannot be measured*³ Example 1 Comparative 1.0Cannot be measured*³ 1.0 Cannot be measured*³ Example 2 Comparative 0.1Cannot be measured*³ 0.1 Cannot be measured*³ Example 3 *¹The printingplate undergone the adhesive strength evaluation test using a printerwas further subjected to aging at 20° C. for 14 days to evaluate theadhesive strength. *²Since adhesive strengths became uneven depending onthe location of measurement, the adhesive strength at each location wasrecorded. *³Since the photosensitive resin was peeled off from thesupport when the flexographic plate was peeled from the plate cylinder,the samples to be aged could not be prepared, and measurement could notbe performed.

INDUSTRIAL APPLICABILITY

According to the present invention, there can be provided aphotosensitive structure for flexographic printing that has a highadhesive strength and excels in production efficiency, and the rejectedplate produced in the production process can be easily reused.

1. A photosensitive structure for flexographic printing comprising alaminate of a support (A), an adhesive layer (B) above said support (A)and a photosensitive resin layer (C) above said adhesive layer (B) whichis different from said adhesive layer (B), wherein said adhesive layer(B) has a thickness of from 0.0001 to 1 mm and comprises a thermoplasticelastomer (a) derived from at least one monovinyl substituted aromatichydrocarbon and a conjugated diene, at least one ethylenicallyunsaturated compound (b) and at least one polymerization initiator (c),wherein said ethylenically unsaturated compound (b) comprises at leastone (meth)acrylate (i) having one or more aromatic rings and one or morehydroxyl groups in the molecule thereof, and wherein said photosensitiveresin layer (C) can be cured by ultraviolet exposure.
 2. Thephotosensitive structure for flexographic printing according to claim 1,wherein said (meth)acrylate (i) comprised of said ethylenicallyunsaturated compound (b) and having one or more aromatic rings and oneor more hydroxyl groups in the molecule thereof has two or moreethylenically unsaturated groups.
 3. The photosensitive structure forflexographic printing according to claim 1 or 2, wherein said(meth)acrylate (i) comprised of said ethylenically unsaturated compound(b) and having one or more aromatic rings and one or more hydroxylgroups in the molecule thereof has a bisphenol skeleton.
 4. Thephotosensitive structure for flexographic printing according to claim 1or 2, wherein said ethylenically unsaturated compound (b) comprises said(meth)acrylate (i) and a polyester(meth)acrylate (ii) having two or moreethylenically unsaturated groups in the molecule thereof.
 5. Thephotosensitive structure for flexographic printing according to claim 4,wherein said ethylenically unsaturated compound (b) comprises said(meth)acrylate (i) and a polyester(meth)acrylate (ii) having two or moreethylenically unsaturated groups in the molecule thereof, wherein theweight ratio (i):(ii) is 0.01:1 to 10:1.
 6. The photosensitive structurefor flexographic printing according to claim 1 or 2, wherein saidphotosensitive resin layer (C) is a mixture of a thermoplastic elastomerderived from at least one monovinyl substituted aromatic hydrocarbon anda conjugated diene, at least one ethylenically unsaturated compound, andat least one polymerization initiator.
 7. The photosensitive structurefor flexographic printing according to claim 1 or 2, wherein saidthermoplastic elastomer (a) in the adhesive layer (B) comprises astyrene-butadiene block copolymer and/or a styrene-isoprene blockcopolymer.
 8. The photosensitive structure for flexographic printingaccording to claim 1 or 2, wherein said adhesive layer (B) is partiallyor completely polymerized by heat energy and/or light energy.
 9. Thephotosensitive structure for flexographic printing according to claim 1or 2, wherein said adhesive layer (B) contains a recoveredphotosensitive resin composition.
 10. The photosensitive structure forflexographic printing according to claim 1 or 2, wherein said support(A) has at least one undercoat layer on the surface of the side on whichsaid adhesive layer (B) is laminated.
 11. The photosensitive structurefor flexographic printing according to claim 10, wherein said undercoatlayer comprises at least one selected from the group consisting of acomposition containing a (meth)acrylate polymer or a copolymer thereofas a major component, a composition containing an aromatic polyurethaneresin obtained from a polyisocyanate containing an aromatic ring and apolyol, as a major component, and a composition containing both as amajor component.
 12. A method for preparing a photosensitive structurefor flexographic printing comprising the steps of forming a support (A),forming an adhesive layer (B) above said support (A) and forming aphotosensitive resin layer (C) above said adhesive layer (B) which isdifferent from said adhesive layer (B), wherein said adhesive layer (B)has a thickness of from 0.0001 to 1 mm and comprises a thermoplasticelastomer (a) derived from at least one monovinyl substituted aromatichydrocarbon and a conjugated diene, at least one ethylenicallyunsaturated compound (b) and at least one polymerization initiator (c),wherein said ethylenically unsaturated compound (b) comprises at leastone (meth)acrylate (i) having one or more aromatic rings and one or morehydroxyl groups in the molecule thereof, and sequentially laminatingsaid support (A), said adhesive layer (B) and said photosensitive resinlayer (C), and wherein said photosensitive resin layer (C) can be curedby ultraviolet exposure.
 13. The method according to claim 12, furthercomprising laminating an adhesive layer (B) that is partially orcompletely polymerized by heat or light.
 14. The method according toclaim 12 or 13, wherein said support (A) has at least one undercoatlayer on the surface of the side on which said adhesive layer (B) isformed, and said undercoat layer contains at least one selected from thegroup consisting of a composition containing a (meth)acrylate polymer ora copolymer thereof as a major component, a composition containing anaromatic polyurethane resin obtained from a polyisocyanate containing anaromatic ring and a polyol, as a major component, and a compositioncontaining both as a major component.
 15. A support base material for aphotosensitive structure for flexographic printing formed by providingan adhesive layer (B) on a support (A), wherein said adhesive layer (B)has a thickness of from 0.0001 to 1 mm and comprises a thermoplasticelastomer (a) derived from at least one monovinyl substituted aromatichydrocarbon and a conjugated diene, at least one ethylenicallyunsaturated compound (b) and at least one polymerization initiator (c),wherein said ethylenically unsaturated compound (b) comprises at leastone (meth)acrylate (i) having one or more aromatic rings and one or morehydroxyl groups in the molecule thereof, and wherein said adhesive layer(B) is partially or completely polymerized by heat energy and/or lightenergy.
 16. The support base material according to claim 15, whereinsaid support (A) has at least one undercoat layer on the surface of theside on which said adhesive layer (B) is provided.
 17. A photosensitivestructure for flexographic printing comprising a laminate of a support(A), an adhesive layer (B) above said support (A) and a photosensitiveresin layer (C) above said adhesive layer (B) which is different fromsaid adhesive layer (B), wherein said adhesive layer (B) comprises athermoplastic elastomer (a) derived from at least one monovinylsubstituted aromatic hydrocarbon and a conjugated diene, at least oneethylenically unsaturated compound (b) and at least one polymerizationinitiator (c), wherein said ethylenically unsaturated compound (b)comprises at least one (meth)acrylate (i) having one or more aromaticrings and one or more hydroxyl groups in the molecule thereof andwherein said support (A) has at least one undercoat layer on the surfaceof the side on which said adhesive layer (B) is laminated, saidundercoat layer comprising at least one selected from the groupconsisting of a composition containing a (meth)acrylate polymer or acopolymer thereof as a major component, a composition containing anaromatic polyurethane resin obtained from a polyisocyanate containing anaromatic ring and a polyol, as a major component, and a compositioncontaining both as a major component.
 18. A method for preparing aphotosensitive structure for flexographic printing comprising the stepsof forming a support (A), forming an adhesive layer (B) above saidsupport (A) and forming a photosensitive resin layer (C) above saidadhesive layer (B) which is different from said adhesive layer (B),wherein said adhesive layer (B) comprises a thermoplastic elastomer (a)derived from at least one monovinyl substituted aromatic hydrocarbon anda conjugated diene, at least one ethylenically unsaturated compound (b)and at least one polymerization initiator (c), wherein saidethylenically unsaturated compound (b) comprises at least one(meth)acrylate (i) having one or more aromatic rings and one or morehydroxyl groups in the molecule thereof, and sequentially laminatingsaid support (A), said adhesive layer (B) and said photosensitive resinlayer (C), and wherein said support (A) has at least one undercoatlayer, and said undercoat layer contains at least one selected from thegroup consisting of a composition containing a (meth)acrylate polymer ora copolymer thereof as a major component, a composition containing anaromatic polyurethane resin obtained from a polyisocyanate containing anaromatic ring and a polyol, as a major component, and a compositioncontaining both as a major component.